Water sensitive carboxyl containing homopolymers or copolymers of unsaturated polymerizable carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like, with other vinylidene monomers are known. These materials are normally prepared by polymerization with a free radical catalyst in an organic medium such as benzene in a stirred vessel. During the course of such polymerizations, shortly after the initiation of polymerization, polymer beings to precipitate from the solution as it is formed and flocculates and forms aggregates. The precipitated polymer forms a slurry in the solvent which often becomes extremely thick, resulting in ineffective mixing, heat build-up and fouling on reactor surfaces by polymer build-up. A further problem is that the solvent is trapped in the polymers during aggregation and removal of such trapped solvents as benzenes is time consuming and difficult. An improved solvent polymerization system is desired.